How do you calculate water discharge cost?

Multiply discharged volume by the sewer rate and your billable discharge share, then add fixed fees. With 1,850 kgal at $6.40/kgal at 100% plus $780 in permit and meter fees, the variable cost is $11,840 and the total is $12,620.

Why is the sewer rate higher than my water rate?

Sewer charges cover collection, treatment, and biosolids handling at the POTW, which is more capital- and energy-intensive than potable delivery. It is common for the discharge rate to exceed the incoming water rate, so reducing discharge often saves more than reducing intake.

What is billable discharge share and why isn't it always 100%?

Many utilities deduct water that never reaches the sewer, like evaporation, product water, or irrigation. A deduct meter or sewer-credit allowance can drop the billable share well below 100%, directly lowering your variable cost.

What is a good water discharge cost per kgal?

There is no universal target since rates are local, but the effective cost per kgal here is $6.82, blending the volumetric rate with fixed fees. Track your own per-kgal figure month over month; a rising number with flat volume usually means fixed fees or surcharges are creeping up.

How much would a 20% flow reduction save?

Cutting 20% of 1,850 kgal removes 370 kgal of billable flow at $6.40, saving about $2,368 per month, or roughly $28,000 a year, while the $780 fixed fee stays put.

Does this include BOD or TSS surcharges?

No. This calculator covers volume-based charges and fixed fees only. If your permit assesses surcharges for high-strength waste, add those separately, because for food and beverage plants they can rival the volume charge.

Environmental Compliance, Waste & Water Management calculator

Water Discharge Cost Calculator

Water Discharge Cost is the total a facility pays its municipal sewer authority or POTW to send process and sanitary effluent down the drain, combining a volumetric sewer charge with fixed permit, meter, and account fees. Plant utility managers, environmental engineers, and finance teams use it to forecast the wastewater line on the utility bill, defend reuse and recovery projects, and catch billing errors. It matters because sewer rates routinely run higher than the potable water rate that delivered the water in the first place, and a metal finishing, food, or beverage plant can move millions of gallons a year. Knowing the all-in cost per kgal also tells you exactly how much a flow-reduction or closed-loop project is worth.

What this calculator does

Estimate water discharge cost from discharged water volume, discharge or sewer rate, applicable share, and fixed environmental fees.
an environmental or operations manager needs to budget or compare water discharge cost
It computes total water discharge cost by multiplying discharged volume by the sewer rate and billable share, then adding fixed permit, meter, and account fees, and also returns an effective cost per kgal.

Formula used

Variable cost = discharged water volume × discharge or sewer rate × billable discharge share
Total water discharge cost = variable cost + fixed permit, meter, or account fees

Inputs explained

Discharged water volume:
Discharge or sewer rate:
Billable discharge share:
Fixed permit, meter, or account fees:

How to use the result

Use it monthly to reconcile the sewer portion of your utility bill, and during capital planning to size the savings from flow reduction, water reuse, or sub-metering of non-discharged water.
It assumes a single flat volumetric rate; it does not model tiered/seasonal sewer blocks or surcharges for high BOD, TSS, or pH that many POTWs levy on top of the volume charge.

Common questions

How do you calculate water discharge cost? Multiply discharged volume by the sewer rate and your billable discharge share, then add fixed fees. With 1,850 kgal at $6.40/kgal at 100% plus $780 in permit and meter fees, the variable cost is $11,840 and the total is $12,620.
Why is the sewer rate higher than my water rate? Sewer charges cover collection, treatment, and biosolids handling at the POTW, which is more capital- and energy-intensive than potable delivery. It is common for the discharge rate to exceed the incoming water rate, so reducing discharge often saves more than reducing intake.
What is billable discharge share and why isn't it always 100%? Many utilities deduct water that never reaches the sewer, like evaporation, product water, or irrigation. A deduct meter or sewer-credit allowance can drop the billable share well below 100%, directly lowering your variable cost.
What is a good water discharge cost per kgal? There is no universal target since rates are local, but the effective cost per kgal here is $6.82, blending the volumetric rate with fixed fees. Track your own per-kgal figure month over month; a rising number with flat volume usually means fixed fees or surcharges are creeping up.
How much would a 20% flow reduction save? Cutting 20% of 1,850 kgal removes 370 kgal of billable flow at $6.40, saving about $2,368 per month, or roughly $28,000 a year, while the $780 fixed fee stays put.

Last reviewed 2026-05-12.